Problem installing co-linear pipe for gas fireplace conversion

[Dw1973]

I want to convert my wood burning fireplace into a gas fireplace. The problem I have is my chimney goes up about 4ft via masonry brick with slotted vents then angles to a pipe going through the roof. Problem I have is the two 3 inch co-linear pipe will not fit through the masonry brick slots shown in the pic attached. Somehow I have to enlarge the slots to accommodate the co-linear pipe for the gas fireplace. Any ideas/recommendations? DW

 

[webby3650]

Those blocks look structural. It's likely that they can't be altered. It's extremely odd to have those blocks in there like that, that's a first for me!

 

[begreen]

That is odd. Are they really masonry blocks or a metal manifold? Try scratching one with a screwdriver.

 

[Dw1973]

I scratched them - they are masonry. Installer said he needs 8 in of space to install the two 3 inch pipes for the gas fireplace. I uploaded more photos of the fireplace.